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To interconnect low voltage solar photovoltaics (PV) with dc system, a dc-dc boost converter is required. To minimize the switching frequency oscillations in solar PV voltage, Aluminum Electrolytic Capacitors (AECs) are connected between solar PV and the converter. Operational life of AECs depend on electrical and environmental parameters and is less than that of solar PV panels. Equivalent Series Resistance (ESR) of AEC increases with life, thereby increasing the voltage ripple across PV terminals. This results in less power extraction from solar PV. This paper proposes a method for health monitoring of AEC using the parameters measured for maximum power point tracking (MPPT) (PV voltage and current). The proposed technique is applicable for both Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM) of operation of the converter. Effect of temperature on ESR is incorporated for accurate determination of the health of capacitor. Key advantage is that no additional current or voltage sensor is required to implement this technique, thereby offering a low cost solution.Further, the proposed technique does not require significant processing capabilities and is implemented in the same digital controller used for MPPT. Detailed simulation studies are carried out and results are included in this paper. A laboratory prototype of dc-dc boost converter is developed for experimentation. Results are in agreement to that obtained from simulation studies.

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Grid tied single-phase solar inverters offer less operational life when compared with the Photovoltaic (PV) panels due to the use of aluminium electrolytic capacitor (AEC). With time, AEC degrades, resulting in an increase in ripple voltage on PV panel. This would reduce the power extraction efficiency of the system, thereby a loss of revenue. This study proposes a simple and cost-efficient online technique for monitoring the health of AECs. The proposed technique suggests evaluating the AEC impedance at twice the grid frequency. Sampling of PV voltage, PV current and inductor current is required to determine the second harmonic impedance of AEC. These voltage and current sensors are present in commercially available solar PV inverters for their control operation. The proposed technique could be extended to other single-phase inverter applications provided that voltage and current sensors are available. Suitable mathematical model of the technique is derived to determine the effect of sampling instant on the accuracy of the results. Criteria for the replacement of capacitor based on impedance monitoring is defined. For validation of the proposed technique, detailed simulation studies are carried out for a single-phase PV system. The technique is verified experimentally on a scaled down solar PV inverter prototype.